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  <section id="module-stringprep">
<span id="stringprep-internet-string-preparation"></span><h1><a class="reference internal" href="#module-stringprep" title="stringprep: String preparation, as per RFC 3453"><code class="xref py py-mod docutils literal notranslate"><span class="pre">stringprep</span></code></a> — Internet String Preparation<a class="headerlink" href="#module-stringprep" title="Permalink to this headline">¶</a></h1>
<p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.9/Lib/stringprep.py">Lib/stringprep.py</a></p>
<hr class="docutils" />
<p>When identifying things (such as host names) in the internet, it is often
necessary to compare such identifications for “equality”. Exactly how this
comparison is executed may depend on the application domain, e.g. whether it
should be case-insensitive or not. It may be also necessary to restrict the
possible identifications, to allow only identifications consisting of
“printable” characters.</p>
<p><span class="target" id="index-0"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc3454.html"><strong>RFC 3454</strong></a> defines a procedure for “preparing” Unicode strings in internet
protocols. Before passing strings onto the wire, they are processed with the
preparation procedure, after which they have a certain normalized form. The RFC
defines a set of tables, which can be combined into profiles. Each profile must
define which tables it uses, and what other optional parts of the <code class="docutils literal notranslate"><span class="pre">stringprep</span></code>
procedure are part of the profile. One example of a <code class="docutils literal notranslate"><span class="pre">stringprep</span></code> profile is
<code class="docutils literal notranslate"><span class="pre">nameprep</span></code>, which is used for internationalized domain names.</p>
<p>The module <a class="reference internal" href="#module-stringprep" title="stringprep: String preparation, as per RFC 3453"><code class="xref py py-mod docutils literal notranslate"><span class="pre">stringprep</span></code></a> only exposes the tables from <span class="target" id="index-1"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc3454.html"><strong>RFC 3454</strong></a>. As these
tables would be very large to represent them as dictionaries or lists, the
module uses the Unicode character database internally. The module source code
itself was generated using the <code class="docutils literal notranslate"><span class="pre">mkstringprep.py</span></code> utility.</p>
<p>As a result, these tables are exposed as functions, not as data structures.
There are two kinds of tables in the RFC: sets and mappings. For a set,
<a class="reference internal" href="#module-stringprep" title="stringprep: String preparation, as per RFC 3453"><code class="xref py py-mod docutils literal notranslate"><span class="pre">stringprep</span></code></a> provides the “characteristic function”, i.e. a function that
returns <code class="docutils literal notranslate"><span class="pre">True</span></code> if the parameter is part of the set. For mappings, it provides the
mapping function: given the key, it returns the associated value. Below is a
list of all functions available in the module.</p>
<dl class="function">
<dt id="stringprep.in_table_a1">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_a1</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_a1" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableA.1 (Unassigned code points in Unicode 3.2).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_b1">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_b1</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_b1" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableB.1 (Commonly mapped to nothing).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.map_table_b2">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">map_table_b2</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.map_table_b2" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the mapped value for <em>code</em> according to tableB.2 (Mapping for
case-folding used with NFKC).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.map_table_b3">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">map_table_b3</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.map_table_b3" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the mapped value for <em>code</em> according to tableB.3 (Mapping for
case-folding used with no normalization).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c11">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_c11</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_c11" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.1.1  (ASCII space characters).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c12">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_c12</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_c12" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.1.2  (Non-ASCII space characters).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c11_c12">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_c11_c12</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_c11_c12" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.1  (Space characters, union of C.1.1 and
C.1.2).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c21">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_c21</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_c21" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.2.1  (ASCII control characters).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c22">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_c22</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_c22" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.2.2  (Non-ASCII control characters).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c21_c22">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_c21_c22</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_c21_c22" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.2  (Control characters, union of C.2.1 and
C.2.2).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c3">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_c3</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_c3" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.3  (Private use).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c4">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_c4</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_c4" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.4  (Non-character code points).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c5">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_c5</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_c5" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.5  (Surrogate codes).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c6">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_c6</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_c6" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.6  (Inappropriate for plain text).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c7">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_c7</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_c7" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.7  (Inappropriate for canonical
representation).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c8">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_c8</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_c8" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.8  (Change display properties or are
deprecated).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c9">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_c9</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_c9" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.9  (Tagging characters).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_d1">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_d1</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_d1" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableD.1  (Characters with bidirectional property
“R” or “AL”).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_d2">
<code class="sig-prename descclassname">stringprep.</code><code class="sig-name descname">in_table_d2</code><span class="sig-paren">(</span><em class="sig-param">code</em><span class="sig-paren">)</span><a class="headerlink" href="#stringprep.in_table_d2" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableD.2  (Characters with bidirectional property
“L”).</p>
</dd></dl>

</section>


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